1. Field of the Invention
This invention relates to an improved explosively actuated fastener system and method of application thereof.
2. Description of the Prior Art
In the past few decades, various forms of explosively actuated fastener systems have been developed to drive components such as fasteners into hard structures consisting of wood, concrete, masonry and steel. A considerable advantage of using such fastener systems has been the small time required for fastening fasteners to hard structures. However, a major common disadvantage is that the fasteners cause high stresses when penetrating into the receiving material in the region of the fastening whereby greater spalling occurs. In addition, explosively actuated fastener systems are relatively complex in construction and costly to manufacture and, due to inadequate venting of their combustion chamber, suffer from disadvantages that they are relatively noisy and tend to jam from a buildup of spent powder.
Explosively actuated fastener systems have been previously divided into two general groups: the low-velocity fastener system (discharging fasteners at a velocity of less tan about 300 ft/sec) and the high-velocity fastener system (discharging fasteners at a velocity of greater than about 500 ft/sec). A drivepin is positioned at the exit end of a cylindrical barrel of the low-velocity fastener system, with a piston located inwardly and spaced from the drivepin and an explosive charge located behind the piston. A drivepin is positioned behind the piston of the high-velocity fastener system. Despite years of development in high-velocity and low-velocity fastener systems, some disadvantages still exist in numerous versions of such fastener systems. Some high-velocity fastener systems still have the disadvantages of high noise level, dangerous free fastener velocity and high degree of spall and ricochet when the drivepin strikes the work surface. Some low-velocity fastener systems still have the disadvantage of high noise level, power limitation, severe spall out in concrete and high incidence of drivepin damage.
With the fastener systems being ballistic in nature and the fasteners attaining free flight, the fastener systems have achieved safety concerns analogous to handling firearms. The present improved explosively actuated fastener system, which is adapted to provide a means for driving a fastener, has the driving capacity of a high-velocity fastener system and the safety of a low-velocity fastener system, in addition to containing a uniquely simple structure with a minimal number of parts among existing similar marketed goods, a low noise level and reduced drivepin and work damage.
Unlike ballistic fastener systems in which fasteners achieve free flight, zero stand-off fastener systems do not achieve free flight of the fasteners. The zero stand-off fastener systems have a handle that is long enough to ensure that the positioning of the fastener and a work surface is sufficiently close to prevent free flight of the fastener. Thus, the fastener enters the work surface directly from the fastener system. A number of poles are attached to the handle to obtain the sufficient length needed by the zero stand-off fastener system to provide a direct entrance of the fastener from the fastener system into the work surface. Thus, by reducing similarities to firearms and by reducing ballistic features, the zero stand-off fastener systems are safer, but often at the expense of sufficient power to achieve the desired holding penetration in a work surface since the presence of the work surface is a necessary prerequisite to actuating the firing of the solid propellant pill. In prior art, as a result of the co-application of the work surface, barrel, solid propellant pill and fastener, with the fastener functioning as a firing pin, a non-ballistic system is provided. Unfortunately, in the prior art fastener systems, the power achieved and hence the degree of penetration of the fastener into the target structure are limited for zero stand-off fastener systems. In the present invention, there is a major increase in the force exerted on the fastener for a set amount of pressure exerted on the handle of the fastener system.
By deleting some steps required in loading, attempts have been made to simplify and speeden up the use of fastener systems. Designs of power loads have been adjusted to lead to a decrease in required parts, and thus a decrease in cost of production, of fastener systems. Lower costs have also served as a goal to be achieved by increasing applications of versions of fastener systems and by increasing variations in structure of each version of the fastener system without departing from the scope of that version.
In addition, fastener systems have been designed to assure control by the user of the distance traveled by the fastener, the speed of the fastener, the power of the fastener and the depth of insertion of the fastener into the work piece, to name a few. It has been desired that such control by the user would be accompanied by as few changes in the fastener system as possible for fasteners of different weight, shape, length, width, thickness, material and other physical and chemical properties. Another factor that is considered in designing fastener systems is the minimization of problems in the application of the fastener system.
As examples, several patents that have been issued in the past few decades and are aimed at improving power loads follow:
In U.S. Pat. No. 5,544,800, registered on Aug. 13, 1996, U.S. Pat. No. 5,497,929, registered on Mar. 12, 1996, and U.S. Pat. No. 5,423,469, registered on Jun. 13, 1995, Armstrong discusses a system for driving a fastener into a work surface. The system comprises a fastener having a penetration end, a shaft and a receptacle head end for receiving a power charge and a tool having a reciprocable firing pin. The tool comprises a barrel including a bore having a muzzle for receiving the fastener, a spring-biased firing pin and an exhaust chamber connected to the bore for receiving exhaust gases.
In U.S. Pat. No. 5,135,150, registered on Aug. 4, 1992, Chun discusses a pole-type powder actuated tool that includes a first pin having a flange at the top end, a second pin having a flange at the top end in contact with the flange of the first pin so that the second pin will move in unison with the first pin, a front barrel for receiving a drive pin and cartridge, a rear barrel for accommodating the second pin and part of the first pin and engaged with the front barrel at one end and with a connecting pipe at the other end, two springs enclosing the first pin and second pin for forcing the two pins to the normal position after fired.
In U.S. Pat. No. 5,016,802, registered on May 21, 1991, Haytayan discusses an explosive actuated extendable driving tool having a housing with a barrel at its front end for receiving a fastening element, with a load chamber in an inner end of the barrel. A manually actuated reciprocatable positioned shaft is slidably received in a retainer that is mounted to the back end of the housing. A muzzle with a self-aligning spall guard and splash guard are mounted to the barrel, with a noise suppression element being contained in a chamber formed between the spall guard and the splash guard. Exits for the discharge of combustion gases and carbon into the noise suppression element are defined by discharge ports formed in the barrel and spall guard.
Clumb, in U.S. Pat. No. 4,899,919, issued on Feb. 13, 1990, patents a self-energizing fastener system which comprises a fastener and a deflagratable propellant pellet.
Hawkins, in U.S. Pat. No. 4,890,778, issued on Jan. 2, 1990, patents a hammer-activated fastener tool for driving fastener projectiles comprising a relatively movable barrel and housing components. The barrel carries a power load chamber body and a relatively movable piston member which in muzzleward movement drives the fastener object and on breechward movement achieves ejection of the spent power load cartridge. The housing carries a movable firing pin assembly.
Hsu, in U.S. Pat. No. 4,830,254, issued on May 16, 1989, patents a two-stage power driving system for powder actuated tools comprising a barrel, a piston, a first stage power load activation means and a power amplifier. The power amplifier accommodates a stacked arrangement of a fastener and a second stage power load.
In U.S. Pat. No. 3,797,721, issued to Clumb on Mar. 19, 1974, an explosive actuated tool for driving fastening stud is patented and comprises a barrel with a bore. Muzzle is provided at one end of barrel and explosion chamber communicates with the bore. Closed gas expansion chamber surrounds barrel and communicates with bore solely through plurality of passageways in barrel adjacent muzzle.
Helderman, U.S. Pat. No. 3,665,583, issued on May 30, 1972, patents a suspension clip structure which includes a center portion and a projecting retaining flange for facilitating the holding of the suspension clip structure on a power actuated tool.
Hsu et al., U.S. Pat. No. 3,514,025, issued on Oct. 30, 1967, present an electrically operated explosively actuated tool using a caseless cartridge.
Helderman et al., U.S. Pat. No. 3,172,123, issued on Mar. 9, 1965, discuss an explosive actuated tool in which a spring-loaded barrel with a bore is forced toward a work surface, thus forcing a fastener into the bore of the barrel. The fastener acts as a firing pin for igniting a power charge disposed at a head end of the fastener.
The above-listed patents and many other similar inventions have been developed, some of which still exist in the market. This invention strives towards providing an improved explosively actuated fastener system and a method of application thereof. Cased solid propellant pills, with coatings qualifying as cases as well, can be separately and individually loaded in the fastener system. (Unless otherwise specified, any reference to "case" in this invention applies to "coating" as well.) In the fastener system, each manufactured version of a cased solid propellant pill may be used with numerous versions of fasteners. By matching a cased solid propellant pill with a chosen fastener and with a selected fastener system, the user may control the distance traveled by the fastener, the speed of the fastener, the power of the fastener and the depth of insertion of the fastener into a work piece, to name a few.